Zentrum für Strahlenschutz und Radioökologie. Institut für Radioökologie und Strahlenschutz

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1 Zentrum für Strahlenschutz und Radioökologie Institut für Radioökologie und Strahlenschutz Leibniz Universität Hannover Leibniz Universität Hannover Radiation exposures in the aftermath of the Chernobyl accident Rolf Michel 14 th Congress of IRPA, Cape Town, South Africa, 9 13 May 2016 Zentrum für Strahlenschutz und Radioökologie Institut für Radioökologie und Strahlenschutz Leibniz Universität Hannover Leibniz Universität Hannover Content A short look back into 1986: radiation exposures & heuristic lessons learnt Retrospective dosimetry in the highly contaminated areas using I-129 The neighbours of Chernobyl: Returning into the evacuated zone Conclusions 1

2 RBMK Reactor of Unit 4 of the Chernobyl NPP: a graphite moderated boiling water reactor In the course of an experiment an uncontrolled power surge occurred due to inherent lack of safety of the reactor type, design faults, management deficits and human misbehavior. The parts of the building shaded in red were blown away in the first explosion. Generator hall Height and length in m. INSAG-7 R. Michel, IRS, Leibniz Universität Hannover The reactor core lay open, a graphite fire burnt and the residual core melted. 5, Bq SSK (2006)

3 Releases of radionuclides from the Chernobyl accident radio-nuclide half-life volatile elements activity inventory April 26, 1986 in PBq emissions activity in PBq emissions in percent of inventory Te-132 3,26 d I-131 8,04 d I-132 2,3 h I ,8 h I-135 6,61 h Cs-134 2,06 a Cs ,0 a intermediate elements Sr-89 50,5 d Sr-90 29,12 a Ru ,3 d > Ru d 860 > 73 8 Ba ,7 d UNSCEAR (2000) radio-nuclide half-life activity inventory April 26, 1986 in PBq emissions activity in PBq refractory elements (including fuel particles) emissions in percent of inventory Zr-95 64,0 d Mo-99 2,75 d > Ce ,5 d Ce d Np-239 2,36 d Pu ,74 a 0,93 0,035 4 Pu a 0,96 0,03 3 Pu a 1,5 0,042 3 Pu ,4 a Cm d 31 0,9 3 noble gases Kr-85 10,72 a Xe-133 5,25 d total De Cort et al. (1998) 3

4 Cs-137 Karte groß 137 Cs Narodici UNSCEAR (2000) Cs-137 fallout > 37 kbq m -2 Regions with 137 Cs deposition densities in km 2 Land Zone IV: Zone III: Zone II: Zone I: kbq m -2 kbq m -2 kbq m -2 kbq m -2 Expected dose 5-30 msv msv msv > 350 msv Russian Federation Belarus Ukraine Sweden Cs-137 deposition densities > 185 kbq/m 2 exist Finland only in small areas in Sweden near Gävle and in Austria near Salzburg. Austria Norway Cs-137 contains 2-4 kbq/m 2 from global fall-out of Bulgaria atmospheric nuclear weapons explosions in the 1960ties. Switzerland Greece Slovenia 300 Italy 300 Moldavia 60 4

5 Rescue teams Liquidators Evacuees Exposed populations Inhabitants of areas with 137 Cs deposition densities of more than 37 kbq m -2 (1 Ci/km 2 ) living in self-sustained families in a rural area without countermeasures. Returnees into the evacuated zones Distant European populations Exposure of the population in contaminated regions with 137 Cs > 37 kbq/m 2 during 1986 to 2005 without thyroid doses The doses during the period 1986 to 1995 make up 66 5 % of the total 70 years committed dose. Region Population Mean individual dose in msv external internal total total Belarus ,1 2,9 8,0 9,8 Russian Federation ,3 2,5 6,8 8,3 Ukraine ,7 6,1 10,8 12,9 Dose : 34 5 % of the total 70-years-dose (UNSCEAR, 2000, 2011; Chernobyl Forum, 2005) R. Michel, IRS, Leibniz Universität Hannover 5

6 Distribution of the affected populations of Belarus, the Russian Federation and Ukraine according to effective dose interval : Belarus, Russian Federation (19 regions) & Ukraine combined. 1E+08 7,0E+07 Number Anzahl der of Personen persons 1E+07 1E+06 1E+05 1,9E+07 6,7E+06 98,000,000 persons 1,6E+06 1,0E+06 4,7E+05 1,2E+05 2,6E+04 1E+04 < > 100 Effective effektive dose Dosis in in msv msv UNSCEAR (2011) R. Michel, IRS, Leibniz Universität Hannover Heuristic rules for dose assessment 1000 total effective dose in msv Germany Range of natural radiation exposures Belarus, Russia, Ukraine Zone IV Zone III Zone II Zone I Average total effective 70- years dose (without thyroid dose) due to the Chernobyl accident in areas with 137 Cs fallout of more than 37 kbq m -2 0,1 0,001 0,01 0, Cs-137 deposition density in MBq m -2 Rural population, , without thyroid doses, podzol chernozem peat without countermeasures. SSK (1996) natural exposures mean natural exposure SSK (2006) R. Michel, IRS, Leibniz Universität Hannover 6

7 Heuristic rules for dose assessment total annual effective dose in msv ,1 0,01 Range of natural radiation exposures Belarus, Russia, Ukraine 0,01 0, Cs-137 deposition density in MBq m -2 podzol chernozem peat Christinovka, Narodici Rayon Zone VI Zone III Zone II Zone I Christinovka 2003 natural exposure mean natural exposure Annual effective dose in 2001 for adults in areas with 137 Cs fallout of more than 37 kbq m -2 without countermeasures assuming exclusively food from local production and total annual effective dose for inhabitants of Christinovka (Handl et al. 2003) SSK (2006) R. Michel, IRS, Leibniz Universität Hannover Inhabitants of areas with 137 Cs deposition densities larger than 37 kbq/m 2 (1 Ci/km 2 ) Street in Narodici, Zhitomir Oblast, Northern Ukraine 7

8 Reference date May 10, 2006 Narodici Sr-90 Atlas Ukraine radioactive contamination (2008) Ambient dose rates measured at Narodici April 27 May 2, R/h = 30 msv/h 1,7 R/h = 17 msv/h 0,6 R/h = 6 msv/h 8

9 The rural population was not warned; there were no countermeasures! Between May 10 and May 28, 1986 only eight settlements were evacuated from zone II. 27 settlements were evacuated between 1989 and 2004 from zone II. A total of 30,908 persons were thus evacuated. Memorial for the evacuees in Northern Ukraine in the municipal park of Narodici Retrospective dosimetry of I-131 by I-129 (T 1/2 = 15,7 Ma) 9

10 I-129 retrospective dosimetry A H D( I) D ( I) DC thyr pre Ch. 131 A129 H thyr : thyroid equivalent dose due to 131 I D( 129 I): measured 129 I inventory D pre-ch. ( 129 I) = mbq m -2 pre-chernobyl inventory DC 131 : aggregated dose factor for 131 I 129 I/ 131 I isotopic ratio of the Chernobyl fall-out Straume et al. (1996) 12 ± 3 A( 131 I)/A( 129 I) = 5, I-129 (T 1/2 = 15.7 Ma) in the Environment total natural I-129 inventory of the Earth: kg (327 TBq) I-129 from Chernobyl ca. 2 kg emissions from atmospheric test explosions: 43 kg 150 kg anthropogenic I-129 emissions from European reprocessing plants until 2000 total free natural I-129 inventory of atmosphere, hydrosphere, pedosphere, and biosphere aerial 263 kg 232 kg liquid 3253 kg 129 I/ 127 I isotopic ratios in environmental compartments? ~ ~ up to? 10

11 Inventories of 129 I and 127 I in seven deep soil profiles from Lower Saxony/DE in comparison to data from Ukraine and Russia and to pre-nuclear data. 127 I 129 I 129 I/ 127 I Ort Geometric mean of German soil profiles in g m 2 in mbq m 2 Isotopic ratio a 3,5 1, ,5 1 7, Zhitomir (1997) + Moscow (1996) 0,52 2, ,6 1 - Pre-nuclear soils: Russia ,084 0,017 1, a ratios in the topmost 30 cm. Michel et al. (2005) I-129 retrospective dosimetry needs radioecological modeling Aggregated dose coefficients for the thyroid gland were calculated by Pietrzak-Flis et al. (2003) using the model CLRP: ( ) 10-7 Sv Bq -1 m 2 for 5-years-old children, ( ) 10-7 Sv Bq -1 m 2 for 10-years-old children and ( ) 10-8 Sv Bq -1 m 2 for adults. Rural self-sustained European population without countermeasures. Michel et al. (2005, 2015) 11

12 E D( I) exp( 2) Expectations of inventories and derived thyroid doses E(D corr (I-129)) E(D(I-131)) Thyroid doses H thyroid in Gy Ort in Bq m -2 in 10 6 Bq m -2 5-years-old 10-years-old adults Medium contaminated areas (zone III) near Korosten Nemirovka Woronewo Kupetsch Tschigiri Highly contaminated areas (zone II) near Narodici Nosdrischtsche Novo Scharno Christinovka Michel et al. (2005) Average thyroid doses (Gy) for the birth cohort in 684 Ukrainian and 458 Belarussian locations with more than 10 measurements of I-131 in human thyroids before May/June An opportunity to validate the results of the retrospective dosimetry. Jacob et al. (2004) 12

13 Sampling locations Distances from Chernobyl: 75 km Narodici 115 km Korosten Michel et al. (2015) Sampling at Schurba in

14 Systematic sampling of 5 samples from each settlement in 2005 Sampling in

15 Cs-137: kbq/m 2 Michel et al. (2015) I-129: mbq/m 2 Michel et al. (2015) 15

16 I-131: 0,9 120 MBq/m 2 Michel et al. (2015) Michel et al. (2015) 16

17 I-131/Cs-137 activity ratios I-131/Cs UNSCEAR (2000) Geometric standard deviations observed for each of the 5 samples taken per settlement. 5 samples per settlement allowed estimating the variability of the fallout as a proxy of the variability of the exposure. Michel et al. (2015) 17

18 Individual doses acc. to measurements of I-131 activities in thyroid glands and calculated mean doses (histogram) for the Ukrainian village Rudka Likhtarev et al., Rad. Envir. Biophys. 33 (1994) 149 Derived thyroid doses for 5-years-old children yellow > 1 Gy red > 10 Gy Michel et al. (2015) 18

19 Michel et al. (2015) Comparison of the results of the retrospective dosimetry with those of direct measurements of the thyroid glands. Michel et al. (2015) 19

20 Comparison of the results of the retrospective dosimetry with those of direct measurements of the thyroid glands. Michel et al. (2015) The neighbours of Chernobyl: Returning into the evacuated zone Christinovka Chernobyl Map UNSCEAR (2000) Christinovka: Typical village in the evacuated zone II, 75 km away from Chernobyl NPP, Narodici rayon All inhabitants were evacuated in 1989/90. Since1995 about 30 families returned to their homes. Except for bread, all foodstuffs are locally produced. 20

21 Nuclide Inventory Cs ±1 MBq/m 2 Sr ±1 kbq/m 2 Pu ±1 Bq/m 2 Pu-239/ ±1 Bq/m 2 Am ,1 ±1 Bq/m 2 Cm ± 2.3 ±1 Bq/m : Investigations of soil profiles, agricultural soils, plants, meat, fish, foodstuffs for 137 Cs, 90 Sr, 238 U, 235 U, 238 Pu, 239,240 Pu, 241 Am, 244 Cm. In addition, personal dosemeter measurements and whole body counting were performed. Christinovka, 2002 Radiation exposure in Christinovka 2002 Annual effective dose in msv Total Mewis (2004) 21

22 Distribution of Pu-238/Pu-239,240 activity ratios in 14 agricultural soils from Christinovka Nuclear weapons fall-out Chernobyl frequency 238 Pu/ 239,240 Pu activity ratio S. Hippler (2006) 70 years committed dose in Sv ( ) Pu-238 Pu- 239/240 Pu-241 Am-241 Sum Ingestion 0,26 0,52 0,31 0,37 1,47 Inhalation 0,0072 0,0115 0,0064 0,0087 0,034 External 0,0000 0,0000 0,0000 0,0026 0,0027 Total 0,27 0,54 0,32 0,38 1,50 Additional dose to smokers 7,2 22,7 13 0,79 43 Adult self-sustained rural population without countermeasures S. Hippler (2006) Christinovka/Zone 2, June

23 Normalized committed effective doses for Plutonium isotopes and Am-241 Pu-238 Pu-239/240 Pu-241 Am-241 Normalized committed effective dose Sv per kbq m-2 Sv per Bq kg-1 7,1 0,63 4,3 0,74 0,082 0,014 5,6 0,81 Adult self-sustained rural population without countermeasures. Hippler (2006) Narodici Pu-isotopes Atlas Ukraine radioactive contamination (2008) 23

24 Conclusions The Chernobyl accident has provided us with a wealth of information about the consequences of a nuclear reactor accident. The past experiences must not be forgotten. They give us heuristic guidelines to estimate the consequences of large area contaminations with Cs-137, Sr-90 and actinides. I-129 retrospective dosimetry is feasible. But it needs an adequate radioecological modeling which takes into account the actual exposure conditions. It is only the second quality compared to direct measurements after an accident. There is still a lot to be done in the surroundings of the Chernobyl NPP. The evacuated and exclusion zones offer unique opportunities to further investigate the pathways of Sr-90 and the actinides through the environment to man. Acknowledgement for the Collaboration D. Beltz, T. Bisinger, W. Botsch, A. Daraoui, Th. Ernst, M. Filss, M. Gorny, J. Handl, S. Harb, S. Hippler, D. Jakob, L. Johannson, K. Klipsch, A. Mewis, R. Sachse, A. Schmidt, C. Schnabel, S. Szidat, L. Tosch, B. J.-W. Vahlbruch, C. Wanke, J.-H. Wicke Center for Radiation protection and Radioecology, now: Institute for Radioecology and Radiation Protection (IRS), Leibniz University Hannover, Germany V. Alfimov, M. Christl, J.M. López-Gutiérrez, H.-A. Synal, L. Wacker Laboratory of Ion Beam Physics, ETH-Zurich, Zurich, Switzerland L.D. Romantschuk State University of Agriculture and Ecology, Zhitomir, Ukraine 24

25 The End 25